Fischer-Tropsch process

ABSTRACT

A Fischer-Tropsch process utilizing a product selective and stable catalyst by which synthesis gas, particularly carbon-monoxide rich synthesis gas is selectively converted to higher hydrocarbons of relatively narrow carbon number range is disclosed. In general, the selective and notably stable catalyst, consist of an inert carrier first treated with a Group IV B metal compound (such as zirconium or titanium), preferably an alkoxide compound, and subsequently treated with an organic compound of a Fischer-Tropsch metal catalyst, such as cobalt, iron or ruthenium carbonyl. Reactions with air and water and calcination are specifically avoided in the catalyst preparation procedure.

This invention was made under DOE Contract No. DE-AC22-80PC30021 and issubject to government rights arising therefrom.

This application is a continuation-in-part of U.S. Ser. No. 741,403,filed June 5, 1985, now U.S. Pat. No. 4,619,910.

TECHNICAL FIELD

This invention relates to a process for the selective conversion ofsynthesis gas to hydrocarbons of relatively narrow carbon number rangesand to catalysts therefor.

BACKGROUND OF THE INVENTION

Production of hydrocarbon liquid fuels from coal may be accomplished, inparty, by the Fischer-Tropsch catalyzed synthesis of hydrocarbons fromsynthesis gas (CO+H₂) produced by coal gasification. The Fischer-Tropschsynthesis (or conversion), however, is unselective in nature, producingmolecules with carbon numbers typically in the range 1-40 in proportionscontrolled by process kinetics. Process efficiency would be enhanced byselective conversion of the synthesis gas to relatively narrow carbonnumber range hydrocarbons within the general range of C₄ -C₂₅hydrocarbons.

Fischer-Tropsch conversion of synthesis gas has heretofore beenconducted both in fixed bed, gas-solid reactors, gas entrained fluidizedbed reactors and in slurry phase reactors. The former is described by H.H. Storch, et al. in "The Fischer-Tropsch and Related Syntheses," Wiley,1951, while the latter is described in Kolbel, et al., Catalysis ReviewScience and Engineering, 1980, 21, page 225, Poutsma (ORNL-5635, 1980),"Assessment of Advanced Process Concepts for the Liquefaction of Low H₂/CO Ratio Synthesis Gas" and Deckwer, et al., Industrial EngineeringChemical Process Design Developments, 1982, Volume 21, pages 222 and231. The latter references in particular indicate the potentialincentive for using high CO/H₂ ratio synthesis gas (sometimes referredto as "syngas") in liquid phase slurry reactors. More recently,Satterfield, et al., Industrial Engineering Chemical Process DesignDevelopment, 1982, Volume 21, page 465, described literature on productdistribution in Fischer-Tropsch syntheses, particularly slurry reactorsusing iron catalysts. All of these analyses indicate that the productselectivity in such syntheses follows a predicted Schulz-Florydistribution, characterized by a chain growth probability factor, alpha,and that any reported deviations in publications concerning theFischer-Tropsch process are probably due to experimental artifacts.

The maximum fuel product fractions predictable from the Schulz-Florydistribution, together with an indication of methane and C₂₆ + fractionare as follows:

    ______________________________________                                        Schulz-Flory Maxima                                                                          C.sub.1 C.sub.5-11                                                                             C.sub.9-25                                                                          C.sub.26 +                                      Alpha  wt %    wt %     wt %  wt %                                    ______________________________________                                        Gasoline Range                                                                          0.76     5.8     47.6   31.8   0.7                                  Diesel Range                                                                            0.88     1.4     31.9   54.1  12.9                                  ______________________________________                                    

In general, prior publications indicate that most Fischer-Tropschproducts adhere to the Schulz-Flory distribution, regardless of catalysttype. Satterfield, et al. specifically concluded that the distributiongenerally held for iron based Fischer-Tropsch catalyst with values ofalpha ranging from 0.55 to 0.94. Short term success in selective syngasconversion, by utilization of a proposed metal particle size effect orby use of CO₂ (CO)₈ on alumina or ruthenium in zeolites of selectivepore size distribution, for example, has been reported by Nijs, et al.,Journal of Catalysis, 1980, Volume 65, page 328 and Blanchard, J.C.S.Chem. Comm., 1979, page 605. However, none of these previous attemptshas produced a stable selectivity over a period of time, the observedselectivity in each case disappearing over a period of hours andreverting to the expected Schulz-Flory distribution.

In addition to the foregoing, the following patents have been consideredspecifically in regard to the patentability of the present invention.

U.S. Pat. No. 4,219,477--Wheelock describes a hydrocarbon reformingcatalyst and the process for its preparation. The catalyst is comprisedof a Group VIII metal, preferably in Group VIII noble metal, depositedon an alumina support previously treated with a solution of Group IV Bcompound (a compound of titanium, zirconium, or hafnium, such as analkoxide according to the specification of this patent); for example,the alumina catalyst base is contacted in a hydrocarbon solution ofzirconium propoxide. In the preparation of this catalyst according tothe Wheelock patent, the alkoxide-treated alumina catalyst base is driedand calcined in a moist atmosphere, treated in an atmosphere of 50-100%relative humidity at 60°-90° F. (sufficient to form a metal oxide) andthen calcined at between 800° and 1,800° F. The Group VIII metal is thenimpregnated into the support in the form of a salt or complex and thecatalyst is dried at 150°-300° F. in the presence of nitrogen or oxygenor both, followed by calcination at 500°-1,000° F. The Group VIII metalimpregnation and subsequent calcination may be conducted in the presenceof oxygen or in an inert gas atmosphere.

U.S. Pat. No. 4,385,193--Bijwarrd, et al. relates to a process for thepreparation of middle distillates by a conventional Fischer-Tropschfirst stage and a hydro-reforming second stage. Suitable catalysts forthe first stage are prepared by impregnation of a porous carrier, withone or more aqueous solutions of salts of Fischer-Tropsch metals andpromoters. The promoters include Group IV B metals (e.g., zirconium) andthe supports include alumina. A particular example iscobalt/zirconium/silicon oxide, prepared by impregnation of the silicawith an aqueous solution of a cobalt and a zirconium salt, followed bydrying, calcining at 500° C. and reduction at 280° C. No indication isgiven in the patent of any selectivity of the catalyst for theFischer-Tropsch reaction.

U.S. Pat. Nos. 3,980,583, 4,393,225, and 4,400,561 to Mitchell, et al.claim catalysts for hydro-formylation and the Fischer-Tropsch reaction,prepared from SiO₂, Al₂ O₃, or an alumino-silicate, which may becombined with a Group IV metal oxide. The support is functionalized withan amine which binds the catalytic Group VIII metal to the surface.

In addition, it is otherwise well-known that ruthenium is useful as aFischer-Tropsch catalyst.

Other recent literature, Basset, J.C.S. Chem. Comm., 1980, 154, hasshown that catalyst prepared by the deposition of [Fe₃ (CO)₁₂ ] onto aninorganic oxide support such as Al₂ O₃, MgO and La₂ O₃ followed bythermal decomposition results in the formation of a metal catalyst witha particle size distribution centered around 14 A°. This catalyst issaid to result in the selective synthesis of propylene from H₂ and COwith propylene selectivities as high as 40% reported. Although thecatalyst gives unusual selectivity to a fairly narrow range of products,its lifetime is short. After about six hours on stream, the catalystbegins to sinter and the selectivity drops off dramatically to give amore conventional Schulz-Flory distribution of hydrocarbons.

According to New Synthesis With Carbon Monoxide, J. Falbe(Springer-Verlag), 1980, metallic ruthenium will catalyze the formationof very high molecular weight hydrocarbons which are similar topolyethylene and are generally referred to as polymethylene. Thisprocess, however, only results in high molecular weights which thepressure is 1,000 to 2,000 atm. (103,000 to 206,000 kPa) and attemperatures of about 200° C.

U.S. Pat. No. 2,632,014 discloses reacting carbon monoxide and hydrogenin CO:H₂ molar ratio of greater than 1:1, in the presence of water and aruthenium catalyst, at a pressure within the range of 100 to 3,000 atm.and at a temperature of 150° to 300° C. Furthermore, the pH must bemaintained below about 1. The catalyst may comprise aruthenium-containing substance deposited on a support such as alumina.

For the synthesis of hydrocarbons from carbon monoxide and hydrogen,numerous patents (such as U.S. Pat. No. 2,284,468) disclose the use of apromoter such as an oxide of vanadium, cerium, iron, thorium, cobalt,chromium, barium, strontium, calcium, manganese, magnesium, zinc, lead,molybdenum, copper, zirconium or aluminum in combination with rutheniumcatalysts.

U.S. Pat. No. 4,088,671 discloses the use of a ruthenium promoted cobaltcatalyst in the synthesis of higher hydrocarbons from carbon monoxideand hydrogen. In a low pressure synthesis gas process the catalyst issaid to result in the substantial elimination of methane in the productwith a simultaneous shift to the production of a higher carbon numberproduct having a lower olefin content. The catalyst may be applied to asuitable support material such as alumina, boria, zinc oxide, magnesia,calcium oxide, strontium oxide, barium oxide, titania, zirconia andvanadia.

U.S. Pat. No. 4,269,784 discloses a homogenous process for preparing C₉to C₆₀ hydrocarbons from carbon monoxide and water using a water-solubleruthenium catalyst. The ruthenium catalyst may be a simple salt such asa halide, acetylacetonate or a complex salt of the formula [RuL₆ ]^(n)where L is a neutral or charged ligand and n is the charge on thecomplex.

British Pat. No. 2,130,113 (published May 31, 1984, priority date Nov.22, 1982) and U.S. Pat. No. 4,499,209--Hoek, et al. discloses aFischer-Tropsch catalyst with C₃ -C₅ selectivity. The catalyst uses asilica base, which is impregnated with an organic solution of, forexample, zirconium or titanium propoxide and calcined. Cobalt is thendeposited, as cobalt nitrate for example, from aqueous solution and iscalcined.

U.S. Pat. Nos. 4,413,064 and 4,493,905--Beuther, et al. (filing dateOct. 13, 1981, issue dates Nov. 1, 1983 and Jan. 15, 1985, respectively)disclose a Fischer-Tropsch catalyst, selective for the production ofdiesel fuel, based on a gamma or eta alumina support on which isdeposited (a) cobalt and a Group IV B metal salt from a nonaqueousorganic impregnant solution or (b) in a two-step process, preferablywithout calcination, cobalt (from an aqueous solution of, for example,cobalt nitrate) and then, from a nonaqueous organic solution, aruthenium salt and a Group IV Be metal oxide, the preferred oxidesincluding ZrO₂ and TiO₂.

Notwithstanding the foregoing teachings, there remains a need for aselective, stable process and catalyst by which synthesis gas may beselectively converted to narrow carbon number range hydrocarbons.

SUMMARY OF THE INVENTION

In accordance with the present invention, synthesis gas, andparticularly CO-rich syngas (i.e. with a CO:H₂ mole ratio of 1:1 to3:1), is subjected to Fischer-Tropsch catalysts, preferably in anotherwise conventional slurry phase reaction, with a stable enhancedselectivity for conversion of the synthesis gas to hydrocarbon productof relatively narrow carbon number ranges by the utilization of aFischer-Tropsch catalyst formulated as follows:

Solid alumina catalyst base particles or alternatively other metal oxidecatalyst base particles such as silica or magnesium oxide are treated inthe absence of air and water with an organic solution of a decomposableorganic compound or salt of a Group IV B metal alkoxide, preferablyzirconium but possibly titanium or hafnium and preferably a propoxide.The treated catalyst particles are then in turn impregnated with anorganic solution of a decomposable organic compound or salt or mixturesthereof of a product selective catalytic metal, namely, cobalt, iron orruthenium. The preferred decomposable compounds are the carbonyls ofcobalt, iron or ruthenium.

The catalyst preparation conditions, the compounds utilized in catalystpreparation, and the slurry phase Fischer-Tropsch reaction conditionsall have some effect on the selectivity of the catalyst in theFischer-Tropsch reaction. In general, the iron carbonyl treated catalysttends to be selective for C₄ and C₅ hydrocarbons, the ruthenium treatedcatalyst tends to be selective for gasoline range hydrocarbons, such asC₅ -C₁₁ compounds and the cobalt-treated catalyst tends to be selectivefor the diesel fuel range of product, namely C₉ -C₂₅.

As contrasted with most of the prior art process and catalysts discussedabove, calcination, oxidation, and water reaction (hydrolysis) with thecatalyst is specifically avoided. The final step in catalyst preparationin each case is essentially a reduction or preactivation of the catalystin a fixed bed reactor, exposing the catalyst to synthesis gas atslightly elevated pressure and temperature, on the order of 100-200 psigand stagewise temperature increases from about 220°-270° C.

The group IV B metal comprises 1-20 weight % of the catalyst and theamount of Fischer-Tropsch catalytic metal, i.e. cobalt, iron orruthenium, is in the range of 0.1-10 wt% of the catalyst.

For a better understanding of this invention, reference may be made tothe detailed description thereof which follows, taken together with thesubjoined claims.

DETAILED DESCRIPTION OF THE INVENTION

The oxide support materials which may be used in the catalyst of theinvention are those inorganic metal oxides which are typically used ascatalytic support materials. For example, such support materials includethe oxides of the metals of Groups II, III, IV, V, and VIA of thePeriodic Table. The oxides of the metals of Groups II, III B and IV Bare preferred. These include alumina, boria, zinc oxide, magnesia,calcium oxide, strontium oxide, barium oxide, titania, zirconia andvanadia. The most preferred support is alumina. A combination of metaloxides, ssuch as silica-alumina, can be employed. The supports can bysynthetically prepared or can be naturally occurring support materials,such as the naturally occurring clays. Specific examples of othersuitable supports include kieselguhr, diatomaceous earth, zeolites,silica, thoria, zirconia, and mixtures of the above.

In making the catalyst of the present invention, the above-referencedsupport material is treated in the absence of oxygen and water, with anonaqueous, typically organic, solution of an organic compound or saltof a Group IV B metal, zirconium, titanium or hafnium or a combinationthereof, compound, preferably an organo compound of zirconium to providea support containing from 1 to 20 wt% of the Group IV B metal. The mostpreferred material is an organo-zirconium compound.

Preferably, the organic radical is an alkoxide radical such as ethoxide,propoxide, isopropoxide and the like. Although alkyl compounds may alsobe used, they are likely to be less effective. In any event, the organicpart of the compound should be decomposable, i.e., adapted to be drivenoff at moderate elevated temperature, i.e. below that of the syngasconversion reaction, to leave a dispersed metallic residue. Examples ofsuitable organo-Group IV B metal compounds useful in he practice of theinvention include zirconium propoxide, zirconium ethoxide, titaniumisopropoxide, titanium ethoxide, hafnium propoxide and the like, ofwhich zirconium propoxide is preferred in the present invention.Typically the Group IV B metal compound is dissolved in a suitablesolvent, such as cyclohexane, which is nonaqueous and nonreactive withthe metal and the catalyst substrate. The catalyst support material ismixed with the solution, then removed and exposed to a vacuum to removeremaining solvent.

Conventional catalyst preparation techniques such as mixing the solidcatalyst support to the point of "incipient wetness" with the impregnantis used both with the Group IV B metal treatment and in the subsequentFischer-Tropsch metal treatment.

The Group IV B metal compound treated catalyst is then treated in theabsence of oxygen and water with a solution of a decomposable compound,typically an organometallic compound, of a selective Fischer-Tropschcatalyst metal, particularly including cobalt, iron or ruthenium. Otherthan carbonyls, which are preferred, compounds which may be used includeacetate, pentanedionate, or other organic complexes or organometalliccompounds of cobalt, iron or ruthenium, which decompose at moderatetemperature, i.e. below that of the syngas conversion process, to leavea metallic residue. Preferably also, the amount of Fischer-Tropschcatalytic metal in the catalyst following such impregnation and dryingis in the range of 0.1-10 wt%.

For impregnation of the catalyst, the metal compound is also dissolvedin a suitable organic solvent such as cyclohexane. This impregnatingsolution is stirred with the previously treated oxide support materialcatalyst. After thorough mixing, the mixture is dried but not calcined.Preferably, drying is performed in vacuum at room temperature.

Thereafter, the catalyst may be conditioned for use by transfer in theabsence of oxygen and water into a reactor, and introduction of theFischer-Tropsch reaction media.

The catalyst of the present invention, produced as described above, maybe utilized in a process, also in accordance with the present invention,to prepare high molecular weight hydrocarbons selectively with respectto the carbon number range of the hydrocarbons. The Fischer-Tropschreaction conditions with which this catalyst may be used are generallyrelatively mild and may be selected so as to produce relatively lowyields of methane while avoiding extremely high pressure processconditions.

In general, the Fischer-Tropsch function of the catalyst is combinedwith the polymerization function of the Group IV B compound impregnanton the catalyst.

The process then comprises reacting a hydrogen-carbon monoxide synthesisgas, preferably in a slurry phase reaction, with a CO to hydrogen ratioin the range of 1:2 to 3:1, preferably about 1.4:1 to 2:1, at a spacevelocity of about 200 hr⁻¹ to about 1000 hr⁻¹, preferably about 300 hr⁻¹to about 600 hr⁻¹, over the catalyst of this invention, for a timesufficient to effect the production of the desired higher hydrocarbonsunder the reaction conditions. Reaction conditions include a temperaturein the range of 200° to 350° C., preferably about 230° to 275° C. and ata pressure of about 100 to 1000 psig, preferably about 250 to 450 psig.While the above reaction conditions may have to be adjusted accordingly,it is possible also in some circumstances to utilize an equivalentamount of carbon dioxide for the carbon monoxide in the synthesis gas.

Specific examples of the present invention, utilizing cobalt carbonyl,ruthenium carbonyl and iron carbonyl, respectively, with zirconiumpropoxide and alumina catalyst support, are described below in Examples1-3, together with representative data therefrom in numerousexperimental runs utilizing materials of these examples. These data areset forth in Tables I-V.

EXAMPLE 1 Catalyst Preparation Zr(OC₃ H₇)₄ /Al₂ O₃

Zr(OC₃ H₇)₄ was reacted by mixture with Al₂ O₃ in cyclohexane in aninert atmosphere until a preselected proportional of Zr(OC₃ H₇)₄ wasdeposited on the alumina. The quantity of Zr(OC₃ H₇)₄ is selected suchthat essentially all of the Al--OH groups on the Al₂ O₃ are combinedwith Zr compounds, in accordance with the following reaction:

    Zr(OC.sub.3 H.sub.7).sub.4 +Al--OH→Al--OZr(OC.sub.3 H.sub.7).sub.3 +C.sub.3 H.sub.7 OH

[Co₂ (CO)₈ ]/Zr(OC₃ H₇)₄ /Al₂ O₃

[Co₂ (CO)₈ ] dissolved in hexane/toluene (volume ratio=1:1) was added tothe Zr(OC₃ H₇)₄ -treated alumina prepared above, after it had been driedin vacuo, in several steps using incipient wetness methods in theabsence of oxygen or water. After each addition of [Co₂ (CO)₈ ] thesolvent was removed in vacuo along with any [Co₂ (CO)₈ ] that did notreact with the surface.

Catalyst Testing Results

The catalyst was transferred to a fixed bed reactor, under an inert gassuch as N₂ in the absence of oxygen or water or preactivated in the gasphase using 20% 1:1 CO/H₂ in N₂ at 175 psig and a GHSV (Gas Hourly SpaceVelocity) of 136 hr⁻¹ (volume gas-slurry/volume catalyst bed/hour),raising the bed temperature in 10° C. stages from 220° to 270° C. Aftercooling in N₂, the activated catalyst (particle size <45 mm) wasslurried in deoxygenated white paraffin oil (as commercially availablefrom Fisher Scientific) and transferred to a 300 ml slurry reactor undera N₂ atmosphere. The final loading was 158 ml of a 15.07 wt% slurrycontaining 21.33 g of activated catalyst.

The slurried catalyst was then contacted with CO/H₂, at mole ratios ofabout 1:1 and 2:1, at 217°-250° C., 300-500 psig, and 310-350 hr⁻¹ GHSVusing stir speeds of 1200 and 1600 min⁻¹. Several main sample points,with associated operating conditions, conversions, and feed ratios arelisted in Table I.

                                      TABLE I                                     __________________________________________________________________________    Slurry Run Summary                                                            15.07 wt % Slurry of 18.0% [Co.sub.2 (CO).sub.8 ]/Zr(OPr).sub.4 /Al.sub.2     O.sub.3                                                                                        Stir                                                         Sample                                                                            Time                                                                             P  T  GHSV                                                                              Speed                                                                             Fractional Conversion                                                                     Feed Ratio                                   #   hr psig                                                                             °C.                                                                       hr.sup.-1                                                                         min.sup.-1                                                                        CO + H.sub.2                                                                        CO H.sub.2                                                                          CO:H.sub.2                                   __________________________________________________________________________     4   25.4                                                                            314                                                                              219.9                                                                            321.6                                                                             1200                                                                              0.201 0.128                                                                            0.272                                                                            0.97                                          8   48.9                                                                            312                                                                              218.9                                                                            318.5                                                                             1200                                                                              0.178 0.106                                                                            0.247                                                                            0.96                                         25  169.4                                                                            300                                                                              246.5                                                                            324.9                                                                             1600                                                                              0.418 0.269                                                                            0.563                                                                            0.97                                         29  193.3                                                                            302                                                                              250.0                                                                            348.3                                                                             1600                                                                              0.266 0.157                                                                            0.483                                                                            1.98                                         __________________________________________________________________________

                  TABLE II                                                        ______________________________________                                        Summary of Slurry Phase Product Distribution Data                             Co.sub.2 (CO).sub.8 /Zr/Al.sub.2 O.sub.3                                              Product Distribution: wt %                                            Samples # C.sub.1 C.sub.2 -C.sub.4                                                                      C.sub.5 -C.sub.12                                                                    C.sub.12 -C.sub.17                                                                   C.sub.18+                             ______________________________________                                         4        15.76   25.42   48.43  10.75   1.66                                  8        15.99   23.64   43.50  13.81   4.32                                 25        10.74   12.13   38.77  18.76  19.30                                 29         5.71    6.34   22.68  28.77  33.50                                 ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        CO Conversion Rates Into Product Fraction                                     (10.sup.-4 mol/min)                                                                                                     Total                                                                         Hydro-                              Sample #                                                                              C.sub.1                                                                              C.sub.2 -C.sub.4                                                                      C.sub.5 -C.sub.11                                                                   C.sub.12 -C.sub.17                                                                   C.sub.18+                                                                           carbons                             ______________________________________                                         4      2.55   4.61    7.72  1.97   0.39  17.24                                8      2.19   3.62    6.61  1.95   0.66  14.85                               25      4.38   5.55    16.66 8.05   9.68  44.32                               29      2.15   2.69    9.19  12.29  15.67 41.99                               ______________________________________                                    

Product distribution data for the Samples listed in Table I aresummarized in Table II. In addition, the rates of CO conversion intovarious product fractions for the samples referred to in Table II arelisted in Table III. These rates may also be considered rates offormation for the various product fractions.

From this and other data, it is apparent that the catalyst wasimmediately active in the slurry phase at 220° C., 314 psig and 0.97CO:H₂, with a CO conversion of 12.58% (fractional conversion×100)corresponding to an activity of 17.24 mol syngas/kg cat/hr (sample 4).Initially, the hydrocarbon product was close to a standard Schulz-Florydistribution, except for a higher CH₄ yield of 15.8% and a low C₂.Approximately 48% of the deficiency in the C₂ hydrocarbon yield wasaccounted for by the production of C₂ oxygenates.

While these initial conditions were held essentially constant for 49hours, the product distribution moved to higher molecular weight (sample8). Although the overall activity decreased linearly by 15.4% over thisperiod, the rates of formation of the C₁₂₋₁₇ and C₁₈ + fractionsremained constant and increased respectively (Table III) correspondingto a progressive increase in the degree of polymerization from 0.73 to0.80.

After 169 hours, with reaction conditions at 247° C. and 0.97 CO/H₂, acatalyst activity of 44.9 mol syngas/kg cat/hr, was recordedcorresponding to an overall conversion of 41.8% and a H₂ conversion of56.3% (sample 25). However, product distribution (up to C₃₆)approximated that predicted by the Schulz-Flory at c=0.87. Although thisvalue of degree of polymerization is the theoretical optimum for themaximum yield of C₁₀₋₂₀ product (40 wt%) from a standard distribution,the anomalously high CH₄ yield of 10.7 wt% reduced the C₁₀₋₂₀ fractionto 30.6 wt%.

Note that Samples 4, 8 and 25 are illustrative of reaction conditionsincluding a CO:H₂ ratio actually slightly below 1:1.

When the CO/H₂ ratio was increased to 1.98 at comparable temperatures,further significant departures from the expected Schulz-Florydistribution appear. For example, the CH₄ yield was reduced from 10.7 to5.7 wt% (Sample 25 compared to Sample 29). With this reduced formationof lighter fractions and corresponding increased rates for C₁₂₋₁₇ andC₁₈₊, a lower overall activity of 30.65 mol syngas/kg cat/hr wasobtained. The deviation from the Schulz-Flory distribution in the dieselfuel range, as shown for example by sample 29, demonstrate selectiveconversion to hydrocarbons in the diesel fuel range. This is indicatedspecifically by the C₁₂₋₁₇ and C₁₈₊ product fractions (28.77 and 30.50wt% respectively), and the overall C₉ -C₂₅ product fraction (72.2 wt%).

In general, this and other data demonstrates selective conversion, at ahigh CO;H₂ ratio, of synthesis gas to hydrocarbons in the diesel fuelcarbon number range. The reduction of product above C₂₆ (as compared toan expected Schulz-Flory distribution) is an important feature of thiscatalyst for operation in the slurry phase. The buildup of undistilledheavier product in the slurry phase, and the need to withdraw slurry andcatalyst to maintain a constant level, is minimized.

The effectiveness of this invention with Co₂ (CO)₈ /Zr/Al₂ O₃ isparticularly notable. This catalyst is highly selective for diesel fuel(typically 67% C₉ -C₂₅, when contacted with 2:1 CO/H₂ syngas in a slurryreactor system). The 67.3 wt% product obtained in the C₉ -C₂₅ rangerepresents a 25% increase over what was previously thought to be a limitof 54.1% imposed by the Schulz-Flory distribution. This is particularlyimportant, since the Fischer-Tropsch product, with its potential forhigh n-alkane yield, appears to be particularly well suited for theproduction of diesel fuel. Fischer-Tropsch catalysts prepared inaccordance herewith, therefore, can overcome the limitations on theyield of product fraction, e.g. fuels or lower molecular weightoxygenates, that were previously thought imposed by the standardSchulz-Flory distribution. The selectivity of the catalyst of thisinvention is retained as a function of time, and deactivation rates arelow. The catalysts of this invention are also capable of acceptingdirectly a high CO/H₂ ratio synthesis gas such as is produced byadvanced generation coal gasifiers. The combination of selectivity,maintenance of that selectivity and the integration of the indirectliquefaction stage with the coal gasification stage that is madepossible by the ability to accept CO-rich syngas directly withoutexternal shift, improves greatly the overall energy efficiency of theprocess.

EXAMPLE 2 Catalyst Preparation [Ru₃ (CO)₁₂ ]/Zr(OC₃ H₇)₄ /Al₂ O₃

The catalyst was prepared by adding a hexane solution of [Ru₃ (CO)₁₂ ]to the Zr(OC₃ H₇)₄ support prepared as described in Example 1 above. Thesolvent was then removed in vacuo and the catalyst protected from airand water.

Catalyst Testing

The catalyst was activated in a fixed bed reactor by reaction with CO+H₂prior to slurrying in the oil in the absence of air. The catalyst wastreated with CO/H₂ =1:1, at GHSV=415 hr⁻¹, P=350 psig and T=240° C. Thisactivation was continued for 190 minutes. The catalyst was then loadedinto the oil under a N₂ atmosphere. The resulting slurry contained 12.22wt% catalyst. The product distributions and catalyst testing results aresummarized in Table IV.

                                      TABLE IV                                    __________________________________________________________________________    Summary of Catalyst Testing Results                                           [Ru.sub.3 (CO).sub.12 ]/Zr(OPr).sub.4 /Al.sub.2 O.sub.3                                 T   P  CO Conv                                                                             C.sub.1                                                                           C.sub.2 -C.sub.4                                                                  C.sub.5 -C.sub.11                                                                 C.sub.12 -C.sub.17                                                                 C.sub.18.sup.+                        Sample #                                                                            CO/H.sub.2                                                                        °C.                                                                        psig                                                                             %     wt %                                                                              wt %                                                                              wt %                                                                              wt % wt %                                  __________________________________________________________________________     8    1.047                                                                             250 310                                                                               6.56 26.09                                                                             27.80                                                                             32.87                                                                             7.62 6.13                                  23    1.019                                                                             280 300                                                                              22.63 27.00                                                                             22.94                                                                             35.65                                                                             9.96 4.46                                  37    2.984                                                                             279.5                                                                             305                                                                               6.71 19.59                                                                             23.15                                                                             40.63                                                                             8.70 7.91                                  41    1.230                                                                             281 500                                                                              29.21 20.55                                                                             20.55                                                                             44.87                                                                             11.07                                                                              2.96                                  53    2.965                                                                             279 750                                                                              10.43 11.55                                                                             18.07                                                                             51.15                                                                             14.06                                                                              5.17                                  __________________________________________________________________________

In summary, when contacted with CO-rich synthesis gas, this catalystdemonstrated a selectivity to produce high yields of gasoline rangehydrocarbons, C₅ -C₁₁. There was also a sharp cutoff at C₂₈ -C₃₀,preventing the formation of heavy waxes. This is an important feature ofthe catalyst forming phase operation, as it minimizes the need forwithdrawal of slurry and catalyst from the reactor.

EXAMPLE 3 Catalyst Preparation and Testing Fe₃ (CO)₁₂ /Zr(OPr)₄ /Al₂ O₃

This catalyst was prepared in a manner analogous to [Ru₃ (CO)₁₂]/Zr(OPr)₄ /Al₂ O₃ and protected from air at all times. Fixed bedcatalytic reaction data and product distribution is shown in Table V.

                  TABLE V                                                         ______________________________________                                        Catalyst: [FE3](CO)12]/Zr(Opr)4/Al.sub.2 O.sub.3                              H.sub.2 /Co: 1/1                                                              Time on Stream: 169 hr                                                        Temperature: 270.4° C.                                                 Pressure: 300 psig                                                            GHSV: 201 hr.sup.-1                                                           Fixed Bed Reactor                                                             n-Alkanes                                                                     Wt.        Mole    1-Alkenes    Branched Isomers                              Carbon #                                                                              %      %       Wt. % Mole % Wt %  Mole %                              ______________________________________                                        1       67.3   18.88   --    --     --    --                                  2       1.27   1.01    11.13 18.01  --    --                                  3       0.53   0.54    8.13  8.77   --    --                                  4       6.40   4.99    22.97 18.58  --    --                                  5       23.41  14.70   3.99  2.58   0.83  0.52                                6       3.54   1.86    3.21  1.73   --    --                                  CH.sub.3 OCH.sub.3                                                                    1.16   1.06                                                           CH.sub.3 OH                                                                           1.92   2.52                                                           CH.sub.3 H.sub.7 OH                                                                   4.77   3.34                                                           ______________________________________                                    

From the foregoing, it is seen that the treatment of the alumina surfacewith Zr(OC₃ H₇)₄ results in a support which, when impregnated with ironas the Fischer-Tropsch catalytic metal, gives selective Fischer-Tropschcatalyst, with selectivity centered in the C₄ -C₅ range.

While the foregoing data are illustrative, the carbon number range ofthe product and the type of carbon products in the present invention maybe varied not only by modification of reaction conditions but also bythe selection of Fischer-Tropsch catalyst metals or metals placed on thecatalyst surface, and also on the ratio of Fischer-Tropsch catalystmetal to Group IV B metal to catalyst substrate.

The concentrations of Group IV B and catalytic metals in the catalystsused in these examples was: (weight percent of total catalyst afterfinal drying and before activation.)

    ______________________________________                                                   Zr   Co         Ru    Fe                                           ______________________________________                                        Example 1    11.87  6.22       --  --                                         Example 2    16.32  --         4.8 --                                         Example 3    27.52  --         --  0.54                                       ______________________________________                                    

The selectivity of the catalyst of this invention is retained as afunction of time, and deactivation rates are low. The catalyst of thisinvention are also capable of accepting directly as high CO/H₂₃ ratiosynthesis gas, such as is produced by advanced generation coalgasifiers. The combination of selectivity, maintenance of thatselectivity and the integration of the indirect liquefaction stage withthe coal gasification stage that is made possible by the ability toaccept CO-rich syngas directly without external shift, improves greatlythe overall energy efficiency of the process.

EXAMPLE 4 Catalyst Preparation [Co(No₃)₂ ]/Zr(OC₃ H₇)₄ /Al₂ O₃

An alumina-supported, zirconium, cobalt Fischer-Tropsch catalyst,designated as Example 4, was prepared to provide a reference point forcomparison with the prior art. This reference catalyst was prepared by amore conventional preparation, similar to the preparation techniquedisclosed in Hoek et al, U.S. Pat. No. 4,499,209, except that an aluminasupport was used instead of the silica support disclosed by Hoek et al.A solution, about 210 cc total volume of 59.6 g of zirconium propoxidein isopropanol, was added to 174.2 g of calcined CatapalT SB q-aluminain two portions with thorough mixing to give incipient wetness. Theimpregnated alumina was allowed to dry in ambient air for two days andthen for three hours at 120° C. in air. 44.1 g of cobalt nitrate wasdissolved in deionized water to give 200 cc of a cobalt nitrate solutionwhich was impregnated into the zirconated alumina in one portion. Theimpregnated material was allowed to dry overnight at room temperatureand then at 120° C. for one hour and was finally calcined in air at 300°C. for six hours yielding 211 g of catalyst. Elemental analysis of thismaterial showed a composition of 4.2 wt% cobalt and 7.1 wt% zirconium.

EXAMPLE 5 Catalyst Preparation [Co₂ (CO)₈ ]/Zr(OC₃ H₇)₄ /Al₂ O₃

A second alumina-supported, zirconium, cobalt Fischer-Tropsch catalyst,designated as Example 5, was prepared according to the procedure inExample 1 of the above-referenced application. Standard inert atmospherehandling techniques were used in preparing this catalyst; exposure tooxygen or water was prevented throughout the preparation. 250 g ofalumina was treated in one portion with a 300 cc solution of 84.2 g ofzirconium propoxide in hexane. After mixing thoroughly by shaking theflask, the hexane was evaporated off in vacuo with slight warming in a40°-50° C. bath. To load the cobalt, a two step addition of 40.0 g ofcobalt carbonyl in hexane was used. The first portion was 350 ccfollowed by a 300 cc second portion. After each portion the remaininghexane was removed in vacuo. After complete removal of the solvent, 366g of a brownish-black catalyst was obtained and was analyzed having acomposition of 4.0 wt% cobalt and 6.4 wt% zirconium.

EXAMPLE 6 Catalyst Preparation [Co₂ (CO)₈ ]/Zr(OC₃ H₇)₄ /SiO₂

A silica-supported, zirconium, cobalt Fischer-Tropsch catalyst,designated as Example 6, was prepared using the preparation methoddisclosed in the above referenced application. 87.2 g of silica weretreated in one portion with a 330 cc solution of 50.8 g of zirconiumpropoxide in hexane. After mixing thoroughly by shaking the flask, thehexane was evaporated off in vacuo with slight warming in a 40°-50° C.bath. To load the cobalt, a 200 cc solution having 17.5 g of cobaltcarbonyl in 60/40 toluene/hexane solvent was used. The toluene/hexanesolvent was removed in vacuo. After complete removal of the solvent, 132g of a greenish-tan catalyst was obtained and analyzed as having acomposition of 3.5 wt% cobalt and 6.6 wt% zirconium.

EXAMPLE 7 Catalyst Preparation [Co(NO₃)₂ ]/Zr(OC₃ H₇)₄ /SiO₂

A silica-supported, cobalt, zirconium Fischer-Tropsch catalyst,designated as Example 7, was prepared using the preparation techniquedisclosed in Hoek et al, U.S. Pat. No. 4,499,209. 117.7 g of silica wasimpregnated with a 350 cc hexane solution containing 64.7 of zirconiumpropoxide in the absence of oxygen or water. The hexane was evaporatedoff in vacuo and the dried material was then exposed to ambient air.31.7 g of cobalt nitrate was dissolved in deionized water to give a 200cc solution which was impregnated into the zirconated silica in oneportion. The material was allowed to dry in vacuo for 16 hours at 25°C., then at 50° C. for 7 hours. The material was further dried at 115°C. for two hours and was finally calcined in air at 300° C. for fivehours to give 144 g of catalyst. Elemental analysis of this materialshowed a composition of 4.6 wt% cobalt and 7.5 wt% zirconium.

EXAMPLES 4-7 Catalyst Testing Results

The catalysts produced in Examples 4-7 were transferred to a fixed bedreactor, under an inert gas such as nitrogen in the absence of oxygen orwater and were activated in the gas phase as follows: hydrogen at 3000hr⁻¹ and 0 psig was passed over the catalyst as the catalyst was heatedto 300° C. at 3° C./min and then maintained there for 16 hours.

Part of the activated catalysts of Examples 4 and 5 were then contactedwith CO/H₂ at a mole ratio of 1:1, at 220° C. and 240° C., and 300 psigin a fixed bed reactor. Unit operating conditions, CO, H₂ and CO+H₂conversions and product selectivity data are listed in Table VI.

Part of the activated catalysts of Examples 6 and 7 were then contactedwith CO/H₂ at a mole ratio of 1:1, at 240° C. and 300 psig in a fixedbed reactor. Unit operating conditions, CO, H₂ and CO+H₂ conversions andproduct selectivity data are listed in Table VII.

After cooling in nitrogen part of activated catalysts of Examples 4, 5and 6 were slurried in deoxygenated white paraffin oil (as commerciallyavailable from Fisher Scientific) and transferred to a one liter slurryreactor under a nitrogen atmosphere. The slurried catalyst was thencontacted with CO/H₂ at mole ratios of 1:1, at 240° C. and 300 psigusing stir speeds of about 1200 to 1600 min⁻¹. Unit operatingconditions, CO, H₂ and CO+H₂ conversions, and product selectivity dataare listed in Table VIII.

                  TABLE VI                                                        ______________________________________                                                       Example 4 Example 5                                            ______________________________________                                        OPERATING CONDITIONS                                                          Temperature: °C.                                                                        220     240     220   240                                    Pressure: psig   300     300     300   300                                    GHSV: vol/hr/vol 1100    1100    1157  1157                                   H.sub.2 /CO Ratio: mol/mol                                                                      1       1       1     1                                     CONVERSION: %                                                                 CO                8      24      16    33                                     H.sub.2          17      50      37    76                                     CO + H.sub.2     13      37      26    53                                     SELECTIVITY: wt %                                                             C.sub.1-4        17      18      47    27                                     C.sub.5-9         2      15      28    21                                     C.sub.10-14      20      15       7    18                                     C.sub.15-21      30      24       9    17                                     C.sub.21-25      12      10       4     6                                     C.sub.26 +       19      18       5    11                                     C.sub.5 +        83      82      53    73                                     ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                                         Example 6                                                                             Example 7                                            ______________________________________                                        OPERATING CONDITIONS                                                          Temperature: °C.                                                                          240       240                                              Pressure: psig     300       300                                              GHSV: vol/hr/vol   1000      1000                                             H.sub.2 /CO Ratio: mol/mol                                                                        1         1                                               CONVERSION: %                                                                 CO                 33        15                                               H.sub.2            63        34                                               CO + H.sub.2       49        24                                               SELECTIVITY: wt %                                                             C.sub.1-4          25        15                                               C.sub.5-9          28        11                                               C.sub.10-14        23        17                                               C.sub.15-21        18        25                                               C.sub.21-25         3        15                                               C.sub.26 +          2        17                                               C.sub.5 +          74        85                                               C.sub.5-25         72        68                                               ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                                        Example                                                                              Example  Example                                                       4      5        6                                             ______________________________________                                        OPERATING CONDITIONS                                                          Temperature: °C.                                                                         240      240      240                                       Pressure: psig    310      300      300                                       GHSV: vol/hr/vol  2.5      1.86     2.0                                       H.sub.2 /CO Ratio: mol/mol                                                                      1        1        1                                         CONVERSION: %                                                                 CO                7        29       26                                        H.sub.2           22       56       56                                        CO + H.sub.2      14       42       41                                        SELECTIVITY: wt %                                                             C.sub.1-4         17       22       23                                        C.sub.5-9         9        28       28                                        C.sub.10-14       10       21       20                                        C.sub.15-21       27       18       19                                        C.sub.21-25       14       6        4                                         C.sub.26 +        23       5        6                                         C.sub.5 +         83       78       67                                        C.sub.5-25        60       73       61                                        ______________________________________                                    

As can be seen from the data listed in Table VI, the present method ofalumina-supported catalyst production is more beneficial for theproduction of Fischer-Tropsch products selective to the light distillateboiling range. This is evident from the fact that at the 240° C.reaction temperature run, the C₂₆ + make for Example 4, according to apreparation similar to Hoek et al, was 18 wt% and for Example 5,according to the preparation of the above referenced application, was 11wt%. A similar comparison is seen in the 220° C. reaction temperaturerun, 19 wt% for Example 4 and 5 wt% for Example 5.

As shown in Table VII, the same benefits are demonstrated for asilica-supported catalyst prepared by the method disclosed in thepresent invention. This is evident by comparing a 2% make in C₂₆ + waxfor Example 6, according to the method of the present invention, with a17% make in C₂₆ + wax for Example 7 produced according to the method ofpreparation disclosed in Hoek et al, U.S. Pat. No. 4,499,209.

Table VIII furthers the evidence of performance for catalysts producedby the method of the present invention is not peculiar to fixed bedapplication but demonstrate the same benefits for slurry reactorapplications.

The present invention has been described with reference to a preferredembodiment thereof. However, this embodiment should not be considered alimitation on the scope of the invention, which scope should beascertained by the following claims.

We claim:
 1. In a process for preferentially converting synthesis gas tohydrocarbons in the C₅₋₂₅ range under process conditions includingCO:H₂: mole ratio 1:1 to 3:1 Space Velocity: vol.hr.vol 200 to 1000Temperature: °C. 200 to 350 Pressure: psig 200 to 1000the improvementcomprising conducting said process in the presence of a catalystproduced by a method comprising the following steps: (a) treating aninert, alumina catalyst base material with a nonaqueous solution of analkoxide from the group consisting of zirconium, titanium and hafnium,and removing remaining said nonaqueous solution; (b) impregnating theproduct of Step (a) with a nonaqueous solution of a carbonyl from thegroup consisting of iron and ruthenium, and removing remaining saidnonaqueous solution; and (c) exposing the product of Step (b) to areducing atmosphere;all while maintaining said material and saidproducts under conditions sufficient to avoid hydrolysis, oxidation, andcalcination thereof.
 2. In a process for preferentially convertingsynthesis gas to hydrocarbons in the C₅₋₂₅ range under processconditions includingCO:H₂ : mole ratio 1:1 to 3:1 Space Velocity:vol.hr.vol 200 to 1000 Temperature: °C. 200 to 350 Pressure: psig 200 to1000the improvement comprising of conducting said process in thepresence of a catalyst produced by a method comprising the followingsteps: (a) treating an inert, silica catalyst base material with anonaqueous solution of an alkoxide from the group consisting ofzirconium, titanium and hafnium, and removing remaining said nonaqueoussolution; (b) impregnating the product of Step (a) with a nonaqueoussolution of a carbonyl from the group consisting of iron and ruthenium,and removing remaining said nonaqueous solution; and (c) exposing theproduct of Step (b) to a reducing atmosphere;all while maintaining saidmaterial and said products under conditions sufficient to avoidhydrolysis, oxidation, and calcination thereof.